Effect of free-air CO2enrichment on grain quality of rice (Oryza sativa) and maize (Zea mays) grown under varying nitrogen levels

Abstract

The production of foodgrains are likely to be affected by increasing atmospheric [CO2] levels with subsequent changes in the grains quality. The objective of the present study was to quantify the interactive effects of increasing CO2 and different levels of soil nitrogen applications on quality of the produce. For this rice, C3 (Oryza sativa L.) and maize, C4 (Zea mays L.) crops were grown under ambient [CO2] (380 ppm, AC) and elevated [CO2] (550 ppm, EC) using free air CO2 enrichment (FACE) with five application levels of nitrogen (N0 = No external supply, N1 = 50 kg ha−1, N2 = 100 kg ha−1, N3 =150 kg ha−1 and N4 =200 kg ha−1). Grainswere sampled at maturityand their starch, sugar, protein and mineral nutrient (N, P, K, Zn and Fe) concentrations were analyzed. Increment in grain yield due to elevated [CO2] was more in rice (∼12%) as compared to maize (∼7%). Similarly, the effect of elevated [CO2] on nutritional quality of rice grains was higher as compared to maize grain under all nitrogen levels. Protein concentration declined both in rice and maize grain under elevated CO2 condition at all nitrogen levels as compared to its ambient CO2 counterparts. However, starch and sugar contents increased both in rice and maize grains under elevated CO2 condition at all nitrogen levels. Grain nutrient concentrations of nitrogen, phosphorus, potassium, zinc and iron were diluted both in rice and maize under EC at all nitrogen levels. In general, the extent of changes in nutritional quality was lower in maize than in rice grain. Despite reduction in protein concentration, the grain protein yield (g pot−1) was increased both in rice and maize under EC. Data from this study indicate that CO2 fertilization has the potential to change both the quality and quantity of C3 (rice) and C4 (maize) crops.